The present invention relates to an electroconductive contact unit assembly which allows the positional precision of the tip of each contact unit to be improved, and is suitable for use in a high frequency probe.
Conventionally, a plurality of electroconductive contact units are arranged so as to form a test unit adapted to simultaneously access multiple points for testing semiconductor products. Such a test unit requires a large number of component parts and the assembly work of the test units tends to be highly complex because a plurality of contact probe units, each consisting of a tubular holder and an electroconductive contact unit received therein, have to be mounted on a support plate one by one. To eliminate such a problem, it has been proposed to laminate a plurality of plastic insulating plates having a plurality of through holes passed across their thickness, and slidably receive an electroconductive needle member in each through hole. The holes of the outer insulating plates are dimensioned to be smaller than those in the middle insulating plates so that a coil spring may be received in each through hole, and resiliently urge the corresponding electroconductive needle member in the outward direction.
In recent years, the need has been created to arrange hundreds and thousands of contact units in a small area, for instance in the order of 10 mm square, due to an increasingly higher level of integration found in semiconductor products that are required to be tested. In case of an electroconductive contact unit using a plastic material for the insulating plates of the holder, the mechanical strength may become inadequate when a large number of holes are formed in a small area, and this may cause a warping of the insulating plates which in turn causes the positional errors in the free ends of the individual electroconductive contact units.
Also, when the electroconductive part of each contact unit is subjected to external noises, it may affect the waveform of the signal that is received from the object to be contacted. Additionally, with the use of increasingly higher frequencies in semiconductor chips, the high frequency signal which is conducted through each contact unit may become a source of noises for external devices.
To eliminate such a problem, the present invention provides an electroconductive contact unit assembly, comprising a holder for guiding an electroconductive needle member for contacting an object so as to be axially moveable into and out of a through hole, and a compression coil spring received in the through hole coaxially with respect to the electroconductive needle member so as to resiliently urge the electroconductive needle member out of the through hole, characterized by that: the holder comprises at least one plate member made of material having a high mechanical strength; and the through hole comprises a needle member guide hole for guiding the electroconductive needle member, and a retaining shoulder for retaining the electroconductive needle member therein against a spring force of the compression coil spring; the needle member guide hole being formed in the plate member, and being in turn formed with an insulating film on an inner circumferential surface thereof.
Thus, because the needle member guide hole is formed in the plate member made of high strength material such as metal, it is possible to ensure a sufficient mechanical strength to the part of the holder provided with the needle member guide holes, and thereby prevent the warping of the plate member so that the positional accuracy of the electroconductive needle members can be ensured. Even when the high mechanical strength material consists of readily available electroconductive metal, the necessary insulation can be effected by forming an insulating film between each electroconductive needle member and the corresponding through hole in spite of the sliding contact between the electroconductive needle member and the needle guide hole.
If only one electroconductive needle member is provided on one end of the compression coil spring for each contact unit, the overall structure of the contact unit can be simplified.
If a pair of electroconductive needle members are provided each on the corresponding end of the compression coil spring for each contact unit, the contact unit can be given with moveable ends at both ends so that the contact unit can be placed between two objects to be contacted (a circuit board to be tested and a testing circuit board, for instance) for conducting the desired testing and measurement.
If the holder comprises a plurality of electroconductive plate members which are laminated one over another, and the inner circumferential surface of the through hole is formed with an insulating film, the plate members forming the needle member guide hole can be processed individually.
By grounding the electroconductive holder or the plate member, the electroconductive member and compression coil spring received in the through hole can be electromagnetically shielded, and are therefore protected from noises.
If the retaining shoulder is formed in an insulating film, even when the needle member guide hole is formed in a high mechanical strength material such as metal, the retaining shoulder may be formed in the insulating film while the through hole is formed as a straight hole in the plate member. Because the retaining shoulder can be made in a relative soft part, the process of forming the retaining shoulder is simplified.
If a pair of plate members made of high mechanical strength material are placed on either side of the holder, and a plate member made of plastic material is interposed between the plate members made of the high mechanical strength material, the weight of the assembly can be minimized in spite of the use of the metallic plate members. In particular, by receiving the compression coil spring in the part of the through hole formed in the plastic member, the plastic member is not required to be processed at any high precision, and the work involved in forming the through hole is simplified.
The features and advantages of the present invention will become apparent from the following description with reference to the appended drawings.